Les relations de l infracapitulum et du coxa 1 chez quelques familles d uropodides (Acariens: anactinotriches). - By uropodid mites, the coxae I are coaptated to the infracapitular cylinder. This trend induces several morphological transformations of the joint. This evolutionary process has been studied in some uropodid taxa. A comparison with non uropodid Gamasida was given. Several types of coxal paraxial groove may be distinguished within the group. It can be assumed that this coxal evolution provides a better protection to the infracapitulum and a strong support to the extremely long chelicerae, especially among the higher uropodid mites.